Mid-air refueling of UAVs is now a reality. In a DARPA press release(pdf) they show a modified F/A-18 running in autonomous mode performing a "probe and drogue refueling" with an airborne tanker. See the video here. Exciting stuff, "I am flabergasted."On the other hand, this means that those autonomous uavs hovering, watching, waiting, never have to land.